Considerable research work has been conducted with the view of furnishing thermally stable, elastomeric polymers for various aerospace seal and sealant applications. To meet the rigid requirements of such applications, a polymer must also retain its elastomeric properties at sub-zero temperatures. Polymers that advance the art in meeting the requirements are disclosed by me in U.S. Pat. Nos. 3,846,376; 3,994,861 and 4,064,109.
In the above-cited patents, fluorocarbon ether bibenzoxazole polymers are disclosed that possess a combination of high thermooxidative stability and low glass transition temperatures. In order to exhibit elastomeric properties, these moderate to high molecular weight polymers must be cured. The preferred method of cure is a magnesium oxide-benzoyl peroxide catalyzed cure through aliphatic or olefinic cure sites incorporated within the backbone of the polymer chain. The benzoyl peroxide and magnesium oxide are admixed with the polymer through milling prior to curing. During curing of the formulated polymers, volatiles are evolved with the result that voids may form in the cured products. Thus, there is a need for a fluorocarbon ether bibenzoxazole oligomer that can be thermally cured without prior admixture of the magnesium oxide-benzoyl peroxide catalyst and without the subsequent evolution of volatiles to an elastomer exhibiting high thermooxidative stability and low temperature flexibility.
It is a principal object of this invention, therefore, to provide fluorocarbon ether bibenzoxazole oligomers with reactive acetylenic terminal groups which make possible a volatile-free cure of the oligomers to rubbery vulcanizates possessing a combination of thermooxidative stability and low glass transition temperatures.
A further object of the invention is to provide fluorocarbon ether bibenzoxazole oligomers which can be thermally cured, thereby eliminating the requirement of employing a curing catalyst.
Another object of the invention is to provide a process for synthesizing the oligomers.
Other objects and advantages of the invention will become apparent to those skilled in the art upon consideration of the accompanying disclosure.